USDA Scientists Developing Rapid Salmonella Test

ATHENS, Ga.Salmonella causes more than 1 million cases of illness each year in the United States; however, researchers at USDAs Agriculture Research Service are working on a potential for quick, easy and reliable detection of Salmonella and other foodborne pathogens with the use of "surface-enhanced Raman scattering" (SERS) technology.

If SERS proves successful for cornering Salmonella, the technique might be used at public health laboratories to rapidly identify this or other pathogens responsible for outbreaks of foodborne illness. The researchers noted SERS may one day be used by food manufacturers in their in-house quality control labs.

In a SERS analysis, a specimen is placed on a surface, such as a stainless steel plate, that has been "enhanced" or changed from smooth to rough. For some of their research, the team enhanced the surface of stainless steel plates by coating them with tiny spheres, made up of a biopolymer encapsulated with nanoparticles of silver.

Rough surfaces, and colloidal metals such as silver, can enhance the scattering of light that occurs when a specimen, placed on this "nanosubstrate," is scanned with the Raman spectrometer's laser beam. The scattered light that comes back to the spectroscope forms a distinct spectral pattern known as a Raman spectral signature, or Raman scattered signal. Researchers expect to prove the concept that all molecules, such as those that make up Salmonella, have their own unique Raman spectral signature.

The idea of using a substrate of silver nanoparticles for Raman spectroscopy is not new. But in SERS studies to detect foodborne pathogens, the use of a surfaceenhanced with biopolymers coated with silver nanoparticlesis apparently novel.

The researchers also found SERS can differentiate between two serotypes of Salmonella entericaEnteritidis and Typhimurium.